The exact mechanism of action is not fully understood, but may involve a reduction in pain mediators (e.g. histamine, prostaglandin E, interleukin, leukotrienes or substance P) produced by the tumour and the inflammatory cells at the interface between the tumour and normal bone and radiation-induced mechanical factors, such as a reduction in periosteal swelling [31]. The gene discussed is TAC1; the disease is neoplasm.